Control system



Dec. 14', 1937. c. G. KRoNMlLLER .2,102,324

` CONTROL SYSTEM Filed June 22,*1935 2 sheets-sheet 1 v SIS A Vzsz Y 131,-' l M-O) B f\4\ ,"32- |25 l y Zi [11s/enter' 9" l l 1 Carl @Mont/Ziller Dec. 14, 1937. c. G. KRONMILLER y 2,102,324

CONTROL SYSTEM Fixed June 22, 1955 l 2 sheets-sheet 2 Inverzzbr Patented @est i4, i935? attain aliases i Y. s Contact. sesame Carl G. Kronmiller, Tmnneapolis, Minn., assigner Minneapolis-Honeyweil Regulator Company, Minneapoiis' Minn.,

Delaware a corporation ,of

application im@ ze, i935, semi No, 27,956

The present invention relates to an improved y automatic control system having particular utility in connection with the control'of heating debut also having utility for controlling any condition or force changing device. This invention is an improvement on an invention disclosed and claimed in application Ser. No. 753,783 led by Arthur C. Grant on November 19, 1934.

One of the objects of the invention is the provision of a control system in which a condition or force changing device is operated intermittently under the control of mechanism actuated in response to changes in the value of a condition or force, preferably produced directly by the condii5 tion or force changing device, as distinguished from mechanism which responds to actual values koi' the condition or force when some other conditionor force is such as'normally to require operation of the condition or force changing device.

Another object of the invention is the provision of a control system for controlling a condition or -orce changing device in response to changes in the value of a condition or force produced by the condition or force changing device or in lresponse f. to changes in the eectiveness of the condition or torce changing device when thelvalue ofi some other condition or force is intermediate; and

varying the operation of the condition or force.

' changingdevice when the value ofsaid other conditioner force rises above or falls below said intermediate value.

A further object ofthe invention is the provision of an automatic control system for control'-l ling a condition or 'torce changing device in which changes in 'a condition of the condition or force changing device or responsive to changes in theeiectivenessvthereof, as distinguished from responsiveness to the actual value of the condition' o or force or its effectiveness. for gradually varying the operation of the condition or force changing itievice;I together with means responsive tosome other condition or force for permitting such operation by saidmechanism when the value of such 45 other condition orlforce is at one value and for preventing such operation when said other condition or force is at some other value. Also. preierably, the arrangement is such as to cause operation of the 'condition or force lchanging device another value.

In the preferred form of the invention, the

" f mechanism responsive to changes in the condition of the condition or'force changingl device pro- 5g duces modulating control, whereas the means rethere is provided mechanismresponsive to` when said other condition or force'is at still device when the value of said other condition is intermediate said two values.

A further object of the invention is the provi- 10 sion of an electrical system of automatic control including a condition or force responsive element which closes rst and second switches upon rise and fall in a condition or force to predetermined values, both said switches being open for interl5 mediate velues of 'said condition or force,v the arrangement being such that a condition or force changing device is operated at maximum capacity upon closure` of one of Asaid switches and is operated at minimum capacity upon closure of the 2 other of said switches, and there 'being other means responsive to changesr inthe eectiveness ofv the condition or force changing device or responsive to changes in some/conditioner force produced by the condition or force changing device or responsive to changes in some condition or force produced by the condition or i'orce changing device takes the form of a variable resistance means but may also take the form of a. switching mechanism which is closed upon a decrease in such eiectiveness of the condition or force. 'Ik'he provision of these means also constitutes objects oi the invention.

Another object of the invention is the provision ofa pair of oppositely acting electrical devices for controlling a condition changing device, to- 40 gether with a current controlling mechanism operated by a pair of means for changing the respective energizations of the devices, one of the means responding tochanges in one condition dition changing device for controlling the control means which in turn operate the condition changing device to maintain the condition at its prevailing value, together with mechanisms mechanically associated with the means to prevent the same from controlling the control means along with means responsive to another condition present invention.

Fig. 2 is a sectional view of one form of a current controlling mechanism which may be used in the system of Fig. l.

Fig. 3 is a front view of the current controlling mechanism of Fig. 2 with the cover removed.

Fig. 4 is a diagrammatic showing of a modified form of the invention.

Referring iirst to Fig. 1 of the drawings, a condition or force changing device is herein diagrammatically shown as comprising an electrically operated valve generally indicated at I6 which may control the lflow of gas to a gas-fired hot Water boiler. The valve I6 is controlled by a condition or force responsive device herein shown as a`room thermostat generally indicated at II. The valve I6. is further controlled by a device generally indicated at I2 which responds to changes in a condition or force produced by the condition or force changing device I6 or responds to changes in the effectiveness of this conditionor force changing device as distinguished from one that responds to the actual values of such condition or force or effectiveness thereof.

The electrically operated valve I6 includesl a valve casing I5 (only partially shown herein) which is provided with the usual valve opening I 6 -that isy adapted to be closed by a valve disc I1. l

The valve disc I1 is carried by a valve stem I8 which is pivoted to a lever I 8 by means of a bracket 26. Lever I9 is pivoted at a point indicated at 2l. The valve disc I1 is biased to closed position by a spring 22; The valve disc I1 is adapted to be moved to open position against the bias of spring 22 by means of a motor comprising a pair of field windings 23 and 24 which operate a motor rotor 25 mounted 4upon a rotor shaft 26. A pinion 21, which is carried by rotor shaft 26, is adapted to drive a main gear 28 through suitable reduction gearing generally indicated at `29. The main gear 28 carries a crank pin 30 which, upon clockwise rotation of main gear 28, is adapted to engage the hooked end 3I of a link'32 which is pivoted to lever I9 at a point indicated at 33. The main gear 28 is secured to a shaft 34 which also carries an operator 3.5. Upon clockwisev rotation of main gear 28, the operator 35 engages and lifts an assembly 36v which includes a balancing contact finger 31 that is adapted to engage a balancing resistance 38. The initial upward movement f assembly 36 allows a limit switch 39 to move to closed position, andwhen the valve has been moved to full open position, the assembly 36 opens a similar limit switch 46. 'Ihe under side of bal;

Ianclngresistance 38 is engaged 'by an adjustable contact linger 4I which, in the present showing -of the invention, is engaging the mid-portioniof balancing resistance 38. The balancing contact'` finger 31, when' moved'downwardly, is adapted to ride upon a cam surface 42 formed on an adjustable bracket43 byl means of which the balancing contact linger 31 is lifted oi of the balancing resistance 38. With the parts adjusted as shown,

the balancing contact finger 31 cannot engage the lower quarter of balancing resistance 36.

The valve I6 isvcontrolled by a balanced relay a exible switch arm yI! are secured to a bracket 5I which is pivoted at 52. The flexible switch arm 56 is adapted to engage a contact 53 whenever plung- 49. 'I'his relatively stiff switch arm 48 and the er 41 is in its central position by reason of solencid windings 45 and 46 being equally or substantially equally energized. When so enoid winding 45 is the more highly energized, then the plunger 41 moves to the left to a further degree and brings stii switch arm 48 into engagement with contact 54. Similarly, when solenoid winding 46 is the more highly energized, then plunger 41 moves to the right of the position shown in the, drawings, and flexible switch arm 56 disengages contact 53.

The valve I6 also includes a recycling switching mechanism comprising two pairs of cooperating switch arms indicated at 65 and 56. 'I'hese pairs of switch arms are adapted to be moved to closed circuit position upon manipulation oi a manually operable member 51 which at the same time is operable to hold the valve disc I1 in a partial open position after having been manually moved thereto upon the occurrence of a power failure, as is well-known in the art. For further details of the construction of valve I6 and its general operation, referencermay be had to the co-` pending application of Lewis L. Cunningham, Se- `rial No. 697,686 which was flied November 11, 1933.

The room thermostat I.I comprises a coiled bimetallic element 66 havingvone of its ends secured to a post 6I. The other end of bimetallic element 60 controls a contact blade 62. When the .room temperature to which bimetallic element 66 responds rises to some predetermined high value of say 72 ',F., contact blade 62 moves into engagement with a contact 63, and when the room temperature falls to some lower value, say '10 F., the

`vthe plug 66 is a. tubular member 61 and mounted on ther tubular member 61 is a screw'threaded mounting sleeve 68. The mounting'sleeve 66 and the .tubular member 61 are held rigid with the plug 66 by means of a screw 68. `Rigid1y secured to the plug 66', vas by soldering, is' a tubular member 16, havingdownturned portions 1I and 12. The outer extremity of the tubular member 16 is secured 'to a spacer 13 which coacts with the tubular member 61 to'support the outer end of the tubular "member 16. The openend oi' the tubular meniber 61 is closed by av cap 14 secured.` thereto as by soldering. A bimetallic coil 15 surrounds the tubularmember 16 and one end thereof is secured to the tubular member 16 and the other end is l Secured to a collar rigidly mounted onv atorsion @groesse rod il. The torsion rod il? extends through an opening in the downturned portion li. The end i the torsion rod 'il abuts against the downturned portion E2 and the collar it is adapted to abut against the downturned portion ill thereby limiting longitudinal movement of the torsion rod Ti. The torsion rod il? extends through the plug to and terminates within the casing d5.

Rigidly secured to the torsion rod lll by means of a screw lg is a collar member 73 so that upon rotation of the torsion rod il, the collar llt-3 is rotated. Also located on the torsion rod il and spaced from the collar lli is another collar ed which is rigidly secured to the torsion rod lll by a screw di. Located between the two collars le and il@ are a lever 82, ariction washer 83, a spring holder t6 and a spring 35.' The spring d5 abuts against the collar it to frictionally engage the lever @2 between the friction washer t3 and collar ed. Therefore, when the torsion rod lli is rotated,

the lever t2 is likewise rotated but if rotation of the lever t2 is stopped, the torsion rod ll may rotate with respect thereto. The collar l@ carries a lever liti upon which is mounteda mercurytube high limit switch @d by means of a' mercury tube clip di.

Secured to the lever t2 by means of screws @o but insulated therefrom is an arm t9 which cariies a slider or contact nger 9i. The slider @l is adapted to engage and slide across a resistance coil t2 mounted on a spool 93. The spool dgt is mounted by means of a screw 9d to a support e5l which is in turn secured to the rear wall of casing t5 by means of screws 96. The support @d also carries adjustable stops 9i which are adapted to be engaged by the lever 82.

ln' operation, the bimetallic helix 151s adapted to be subjected to some heater condition such, for

instance, as the temperature of the hot water in a hot water boiler. It willfbe noted that the lever @t and consequently the mercury tube switch 8d are directly secured to the torsion rod ll and move in conformity therewith so that when a predetermined high vtemperature affects the bimetallic helix i5 to rotate the torsion rod il in a counter-clockwise direction as viewed in Fig. `3,

the mercury switch Stwlll be moved to open contact position. Therefore, the mercury svntch ed is adapted to'perform a high limit function as will be set out more fully hereafter. As viewed in Fig. 3, the contact iinger or slider 9i is located midway of the resistance coil t2 and upon an increase in temperature aiecting the bimetallic helix lo, the slider di is moved to the right and umn a decrease in temperature, the slider di is moved to the left. AIl? the temperature aecting the bimetallic helix i5 increases more than a predetermined amount, the lever 82 abuts against..

the adjustable stop o? to prevent further counterclockwise movement thereof and to cause slipping.

between the torsion rod il and the lever 92. Likewise, ii the temperature aiecting the bimetallic heiix l5 decreases more than a predetermined amount, the lever d2 abuts the other' adjustable stop @l and the torsion rod il moves with respect to the lever t2. @rom this it follows that a predetermined diierential inv temperature is required to move the slider @i across the resistance coil @E but due to the slip friction connection between the lever 82 and the torsion rod Ti, the differenf.

tial in temperature may occury at any temperature value. Therefore, the slider 9i is" moved inre-l sponse to changes in a condition or force and not in responseto the actual value of the conditiom itself. However.. the mercury switch et is moved in. response to the actual value of the condition.

Referring speclii'ically to Fig. 3, the lever dit is provided with upwardly and outwardly extending abutments te and ed. Spaced lfrom these abutments 9d and @d are two bmetallic elements w@ and iti, respectively, which are Secured to plugs lo@ by means of screws loo. The screws idd also secure the plugs idd lto resilient brackets iut which are secured to and spaced from the top wall of casing @d by means or screws itl and spacers Miti. Also mounted on the plugs ltd by means of screws i il are loimetallic elements lo@ s and liti. The outerends of these bimetallic elements it@ and titi are secured to adjustable anchors itl?. Electric heaters iii@ and S33 are positioned adjacent to or around the bimetallic elements it@ and loi, respectively. When the heater it@ is energized, the himetallic element itil iiexes inwardly to engage ther/abutment et to move the slider @i to the extreme right of potentiometer coil t?. lIn a like manner, when the heater idd is energized, the bimetallic element lili iiexes to engage the abutment @d to move the slider @i to the extreme left of the potentiometer coil iid. The bimetallic elements tot and il@ associated with the bimetallic elements it@ and iti, respectively, operate in opposition to birnetallic elements it@ and iti to prevent movement of the lower ends of the'bimetallic elements it@ and lili with respect to the abutments @d and @d upon changes in ambient temperature existing within thev casing '55.

Specifically, upon an increase in ambient temperature, the centers of the bimetallic elements its and lit are bowed upwardly and by reason of the resilient brackets me, the bimetaliic eleand il@ is equal to the inward movement of the bimetallic elements. it@ and iti caused by the ambient temperature flexing these elements, therefore, regardless of the ambient temperature within the casing t5, the lower extremities of the bimetallic elements ido and iol are maintained inthe same position.

Referring now to Fig. 1, line wires 22 and i23 leading from some source of power, not shown.. are designated at iat and ld. A primary iid of a step-down transformer 826, having a secondary 025 is connected across the line wires i 22 and 23. One end of the secondary H25 is connected to one of the electrodes of high limit switch 8d by means -of a wire i2?. The other electrode of high limit throug'h the limit switch ed byineansof wires 038;

and i3? .and the same endoil eld winding 2li is connected to contact 53 through the limit switch' d@ by means of wires les and H39. 'One side `of secondary E25 is also connected `to one end or the solenoid coil 4d by means of wire i2'i, high limit switch 3S, wire H28, and wire idd, While the other Q side of the secondary 82o is connected `to one end i of solenoid winding es by wires ser and m. The

junction of solenoid windings 'd5 and it is connected to the balancing contact finger el and to the eld winding 23 is connected to contact 54j connected to a small number of turns of solenoid winding. 25 by a wire |5|. One end of solenoid winding 45 is connected to one end oi' the balancing resistance 3 8 and one end of the potentiometer coil 9,2A through a protective resistance |52 by means ofwires |53, |54'and |55.- Similarly,

oneencl of solenoid winding 46 is connected vto the other end of balancing resistance 38 and the other end of potentiometer coil 92 through a protective resistance |58 by means of wires |59, |60 and |6|. Bracket 43 is connected to contact nger4| by means of wires |63.

A primary |65 of a step-down transformer |66, having a secondary |61 is connected across the line wires |22l and |23. One end of secondary |61 is connected to one end each of the electric heaters |02 and |03 by means of `Wires |66, |69 and |10. The other end of the electric heater |02 is connected by a wire |1| to the contact 63 and the other end of the electric heater |03 is connected bya wirev |12 to the contact 64. The post 6| of the thermostat is connected by a wire |13 to the other end of the secondary |61.

With the parts in the position shown in Fig. l, the room temperature is intermediate 70 and 72 since contact blade -62 is intermediate ccntacts 63 and 64. The boiler temperature is likewise intermediate and the contact finger or slider 8| is shown engaged with the mid portion of the resistance coil 92.` As a result, the balancing con-k tact nger 31 is engaged with the mid portion of balancing resistance 38 and the solenoid windings and 46 are substantially equally energized so that flexible switch arm is engaged with contact 53. The valve is therefore half open and is held in' half open position by reason of energization ofv field winding 24,'the circuit for which is as follows: secondary |25 of transformer |26, wire |21, mercury switch 68, wire |28, wire |29, wire |3|, field winding 24, wire |38, limit switch 39, wire |39, contact 53, iiexibie switch arm 50,

wire |5I, a small-number of turns of solenoid winding 45, wire |4| and wire |32 back to the secondary |25. The flow of current through the small number of turns of solenoid winding 45, upon engagement of flexible switch arm 50 with contact 53, increases the contact pressure between the flexible switch arm 50 and the contact 53 as willy become apparent hereinafter. It should be pointed out here that the two field windings 23 and 24 operate rotor 25 in the same direction wherein one of these field windings when energized is capable of holding valve disc |1 in any position to which it is moved against its biasing spring 22 and the energization of both of these field windings at the same time is sufficient to lift the valve disc |1 against the bias of spring 22.

As long as the room temperature remains intermediate 70 and 72, small fluctuations in boiler temperaturewill result in movement of the contact finger or slider 9| along resistance coil 92. Assuming there is a slight fall in boiler ternperature so that the contact finger 9| moves along resistance' coil 92 toward the left hand bend thereof, the' voltage Adrop across solenoid winding 45 will be increased and the voltage drop across solenoid winding 46 will be decreased whereupon plunger 41 will move further to the left flexing switch arm 50 and bringing switch arm 48 into engagement with contact 54. winding 23 will then 4be energized 'as follows: secondary |25, wire. |21, high limit switch 66, wire |28, wire |29, wire |30, field winding 23, lwire Field |36, limit switch 40, wire |31, contact 54, switch arm 48,'wire 15|, a small number oi turns of solenoid winding 45, wire |4|- and wire |32 back to the secondary |45. 'Ihis ,second circuit through the small number of turns of solenoid winding 45 will increase the contact pressure between switch arm 48 and contact 54. Energization of field winding 23 will cause rotation of motor rotor 25 in such direction as to rotate main gear 28 in -a clockwise direction to raise further the valve disc |1, it being remembered that iield winding 24 is still energized. Such clockwise rotation of main gear 28 also moves balancing contact finger 31 upwardly along balancing resist.- ance 38 and this movement continues until such time as the voltage drops across solenoids 45 and 46 are again substantially equalized whereupon plungerI 41 will return to the position shown in Fig. 1 of the drawings wherein switch arm 48 is disengaged from contact finger 54 but iiexible switch arm 50 is engaged with contact 53. The field winding 23 is thereby deenergized but the field winding 24 remains energized. As heretofore explained, this single field winding is not sufficient to raise the valve so the opening movement of the valve ceases but this energization of field winding 24 maintains the valve in its new position. In ,the event the boiler temperature continues falling until contact finger 9| reaches the left hand end of resistance coil 92, then the valve disc |1 will open fully, the assembly 36 will engage the upper arm of limit switch 40 and open the same to ,d'eenergize field winding 23 whereby the valve will be held in its full open position by the energization of field winding 24.

WheneverA the boiler temperature rises, the contact finger 9| will move along resistance coil 92 toward the right hand end thereof, thereby increasing the voltage drop across solenoid winding 46 and decreasing the yvoltage drop across solenoid winding 45. Under these` conditions, flexible switch arm 50 is moved from engagement with contact 53 whereupon field winding 24 is deenergized as well as field winding 23. The valve disc |1 is therefore moved towards closed position under the bias'of spring 22. At the same time, counter-clockwise rotation of the actuator 35 allows balancing contact finger 36 to move downwardly along balancing resistance 38 until a point is reached wherein the voltage drops across solenoid windings 45 and 46 are again equal and flexible switch arm 50 is moved into engagement with contact 53. When this occurs, the field winding 24 is again energized to prevent further closing movement of the valve f sulting current fiows through the small number y.described and increases the contact pressure between fiexible switch arm 50 and contact 53 to prevent chattering of the contacts.

As the' boiler temperature continues to drop, this action will be repeated until the contact finger 31 rides up the cam surface 42 at which time balancing contact finger 31 will be moved from engagement with the balancing resistance 33: When this occurs, the balancing contact finger- 31 is electrically connected-to the center of balancing resistance 36' by the contact finger 4| and wire |63. Inasmuch as the contact finger 9| is near the right hand end of resistance coil 92 at this time which would require movement of balancing finger 31 near the lower end of balancing'resistance 38 to rebalance the energiza` tions of solenoid windings 45 and 46, it will be 75 -izcipossible to rebalance these energizations whereby emble switch arm 56 will remain disengaged from contact 53 and the valve will move to fully closed position. In this mannen. when the valve reaches some minimum position during closing movement the valve completely closes, thereby eliminating danger of a pop-back into the furnace by reason of the burners being unable to handle such a. small iiow of gas. Movement of the valve to its fully closed position under the bias of spring 22 imparts sumcient momentum to the main gear 22, the motor rotor 25 and the gear reduction 2d to cause these parts to' rotate a small amount after the valve disc Il bef comes seated wherefore the crank pin moves a small distance away from the hooked end ill of the link 32. Also, the assembly 36 moves the lower 'arm of limit switch te and opens the same thereby preventing energization of eld winding 2d.

Now if the boiler temperature again Yrises so that the contact iinger 9i moves'along resistance. coil 62 towards the left hand end thereof, solenoid windinglt will remain more highly energized than solenoid winding t6 until the contact iinger @t reaches the middle of resistance coil 92. This is because balancing contact inger 313s now electrically connected to the center of balancing resistance 38 by the contact iinger 4I and wire E53.

`cient to rotate main gear 28 in tion and bring crank pin 30 When the 'contact finger 9| reaches the middle of resistance coll 92 so that the solenoids #i5 and i6 are equally energized, flexible' switch arm 50 will be moved into engagement with contact 53 but field winding 26 will not be energized since -limitlswitch Bil is opened. Upon 'movement of contact finger 9| past the center of resistance coil 92 toward the left hand end thereof due to further lowering of the boiler temperature, 'the Voltage drop across solenoid winding will become larger than the voltage drop across solenoid winding 46 whereupon switch arm 48 moves into engagement with contact 5.4 and energizes field winding 23 in the manner heretofore described. This energ'lzation of eld winding 23 will be suia clockwise direcrinto engagement Awith hooked link 33 since during this time there is substantially no load upon the motor. Such movement of main gear 28 lifts assembly 36 a slight amount through actuator 35 so that limit switch 39 closes whereupon field winding '24 is also energized. The energization of 'eld windings 23 and 24 continues rotation of main gear 28 whereupon valve disc |1 is raised against the resistance of its spring 22. The valvev will therefore bev raised to a little more than half open position in order to bring balancing contact iinger 31 slightly past the center portion yof bali ancingl resistance 38 in order to rebalance the voltage drops across solenoid windings 45 and 46 so as to disengage switch arm 48 from` contact nger 54 in the manner heretofore described.`

- During this upward movement of balancing contact finger 31, it rides off the cam'surface 42 whereupon the c'ontact iinger 4| -and wire |63 no longer electrically connect balancing contact iinger 3T to the mid. p0rtion of balancing resistance 38. It will therefore be noted that when the valve is closed, it can vonly be open when the demand for heat is suiiiciently great as to result in a. relatively large opening of the valve. Inthis manner, a relatively large initial ow of gas is supplied to the burner so as to prevent a are back into the mixer. The amount of initial openl92. When the contact nger 9| has moved Just -energization of the electric heater |03 which ing can be varied by varying the position oficontact iinger 6| along balancing resistance 38.

From the above, it will be seen that whenever the room temperature is intermediate, the contact linger 6i and its associated resistance coil 92 will modulate the position of the valve disc il to maintain the boiler temperature` at Whatever value it may happen to be. Now if the 'room temperature should rise so as to bring contact blade 62 into engagement with contact 63, acircuit is completed from the secondary 61 of stepdown transformer it through wire 73, post iii, thermostat 6d, blade 62, contact 62, wire lli, heater |02, wire It@ and wire 68 back to the secondary itl. Completion oi this circuit causes energization of heater m2 to flex the bimetallic element I0@ inwardly. The bimetallic element |00 thereby engages the abutment 93 to move the' contact nger di to the right hand end of thev resistance coil e2. Movement of contact nger di to the right hand end of resistance coil 92 short-circuits the solenoid winding i5 whereby the flexible switch arm 5d is moved out of engagement with the contact 53 to deenergize the iieldy windings 23 and 26 to permit the spring 22 to close the valve disc il. In this manner, a rise in room temperature to .or above 72 causes positive closing movement of valve disc l? and prevents the further supply of heatr to the room. When the room temperature decreases to a value less than 72 as a result of stopping the supply 4oi" heat to the room, the thermostat il will assume a position shown in Fig. -1 to break the circuit of the electric heaterg|02 to allow the bimetallic element |06 to disengage abutment 96. Due to the fact that the room thermostat II has Yshut oi`1` the supply of heat to the boiler, the kboiler temperature will drop and as the boiler temperature so drops, the contact -nger 9i is moved towards the left across the resistancecoil beyond the mid position ofthe resistance coil 92 in va mannerJ described hereabove, thesolenoid winding 45 is energized more than thesolenoid winding 46 to move. the switch arm's 48 and 50 into engagement with the contacts 54 and 53 to energize the field windings 23 and 24 to lift the valve disc |1irom its seat and thereby supply fuel to the boiler. The valve I1 will then remain under the control of instrument I2 to maintain the boiler temperature at the value at which the room thermostat I I was` satisfied. `By reason of the control of the boiler by the instrument .|2 in this manner to maintain the temperature of the boiler at this new value, the room temperature will be maintained between and 72.

VIf the room temperature should fall below 70, the bimetallic element 60 moves the blade 62 into engagement with the contact 64 to complete a circuit fromV the secondary |61 of the step-down transformer |66 through wire |13, post 6|, bi- .i metallic element 60, blade 62, contact 64, wire-l |12e heater |03, wire |10, and wire |68 back to the secondary |61. Completion of this circuit causes exes the bimetallic element |0I into 'engagement with abutment 99 to move the contact nger 9| to the left hand end of the resistance coilA 92. Movement of contact finger 9| .to the left hand end of resistance coil 92 causes'short-circuiting of the solenoid winding 46 to move the switch ar'ms 48 and 50 into engagement with the con-l tacts 54 and 53. This causes energization of both field windings 23 and `24 in the manner above described to completely open the valve disc I1.

Complete opening of the valve disc. |1`raises the temperature oi the boiler and supplies more heat to the room. When the temperature of the room has risen above '10 by reason of'this additional supply of heat, the blade 62 moves out of engagement with the contact 64 to deenergize the heater |03 to move the bimetallic element |0| out of engagement with the abutment 99. After the room thermostat has been satisfied, the boiler temperature will continue to rise and move the contact linger 9| from its left hand position toward the right. Movement.` of the contact linger 9| towards the right, increases the voltage .drop acroSS the solenoid winding 46 to move the switch arms 48 and 50 from engagement .with the contacts 54 and 53 to deenergize the eld windings 23 and 24 to move the valve disc I1 away from its full open position to an intermediate position to decrease the temperature of the boiler water. The valve disc I1 and therefore the temperature of the boiler is placed under the control of instrument I2 and the boiler water temperature is maintained at substantially this `new temperature value. In

this manner, the room temperature is maintained between and 72.

If the temperature of the boiler should become excessive, then high limit mercury switch 88 is tilted to an olfI 'position to break circuit to the valve motor and cause deenergization of the field windings 23 and 24 whereupon the spring 22 moves the valve disc I1 to a closed position until -the temperature of the boiler decreases below the high limit value. When the temperature of the boiler decreases to normal, the mercury switch 88 is tilted to circuit making position and the normal mode of operation outlined above is continued.

From the above it is seen that when the room temperature is below a predetermined value, the valve disc |1 is opened to completely energize the boiler to supply heat to the room and that when the room temperature rises above a predetermined high value, the valve disc |1 is closed to deenergize the boiler and prevent the further supply of heat to the room. It is also seen that when the room temperature is intermediate these two predetermined values, the valve is under the control of instrument I2 and responds to. changes in the temperature of the boiler so that the boiler is maintained at a temperature which will maintain the room temperature between the predetermired room temperature values.

Referring now to Fig. 4, I have 4shown 'a modi-.- fled form of my invention wherein the motor for operating a valve is intermittently energized and deenergized to intermittently open and close the valve instead of modulating the valve as in the previous modification. In this modication, the instrument responding to changes in boiler temperature is identical with that in the previous modification with the exception that the instrument operatesopen contact switches instead of a contact nger Acooperating with a resistance coil. The instrument responding to changes in boiler temperature is also controlled by the room temperature in identically the same manner as in the previous modification.

Line wires |15 and- |16, leading from some Y source of power, not shown, and the transformer |86 supplying energy to the heaters |02 and |03 under the control of the room thermostat is connected across these line wires. A relatively rigid blade and a relatively exible blade |8| are connected to but insulated from the lever 82 operf gage a contact |82 and the flexible blade |8| is adapted to engage a contact |83. The distance between the contact |83 and the iiexible blade |8| is less than the distance between the contact |82 and the flexible-blade |80 so that upon a decrease in temperature, the contact |83 is ilrst engaged by its blade and then the contact |82 by its blade. A primary |84 of a step-down transformer |85 having a secondary |86 is connected across the line wires |15 and |16. A relay coil |81 controls the operation ofswitch arms |88 and |89 so that upon energization of the relay coil |81, the switch arms |88 and |89 are moved into engagement with contacts 90 and |9|, respectively, and upon deenergization of the relay coil |81, the switch arms are moved out of engagement with their respective contacts by means of gravity or springs or other means, not shown. One end of the secondary |86 is connected by a wire |92 to the contact |83 and the contact |82 is connected by a wire |93 to one end of the relay coil |81. The other end of the relay coil |81 is connected by a wire |94 to the other end of secondary |86. The blades |80 and I8| are connected by a wire |95 to the contact |90 and the switch arm |88 cooperating with the contact |90 is connected by a wire |96 to the relay coil |81. The switch arm |89 is connected by awire |91 tothe line wire |15 and the contact |9| cooperating with the switch arm |89 is connected by a wire |98 to a ,motor |99. 'I'he motor |99 isin turn connected by a wire 200 to the line wire |16. The motor,

|99 may operate a valve so that upon energization of the motor the valve is opened and upon deenergization thereof the valve is closed by means of a biasing means, such as a spring. Such a motor-operated valve is old in the art and a further description thereof is not considered necessary. The motor |99 may also operate an oil burner or a Stoker in the manner which is known in the art.

When the boiler temperature decreases, the flexible switch arm |8| is moved into engagement with the contact |83 and upon a further slight decrease inboiler temperature, the rigid switch arm |80 is moved into engagement with' the contact |82 to complete a circuit from the secondary |86 through wire |92, contact |83,

switch arm |8I, switch arm |80, contact |82, wire |93, relay coil |81 and wire |94 back to the secinto engagement with the contact |90 completes a holding circuit from the secondary |86 through wire |92, contact |83, blade |8I, wire |95, contact |90, switch arm I 88, wire I 96, relay coll |81 and wire |94 back to the secondary I 86 to maintain the relay coil |81 energized until the boiler temperature has increased a suiiicient amount tobreak contact between the contact |83 andthe switch arm I8I. Movement of switch arm |89 into engagement with contact |9I completes a circuit from the line wire |15 through wire |91, switch arm |89, contact |9|,wire |98, motor |99 and wire 200 back to the line wire |16 to cause energization of the motor |99 to open a valve or to operate an oil burner or a stoker. temperature has risen a predetermined amount 4due to the operation of motor 99, the switch arms |80 and |8| are moved out of engagement with contacts |82 and |83 to deenergize the relay |81 to move the switch arm |89 out of engagement with the contact |9| to stop operation of When the boiler the motor it@ and consequently. stop operation of the oil burner or stolrer or to cause closing of the valve. Therefore, when the roorn temperature is between '30 and 72, the' motor it@ is intermittently operated to maintain the boiler water temperature atpredetermined values.

As in the previous modiiication, as the room temperature rises above 72, the heater ibi is energized to cause the bimetallic element it@ to engage the abutment 38 to open the switch contacts to deenergize the relay itl to close the fue] valve or stop operation ci the ruel burner or Stoker. Likewise, when the room temperature decreases below the heater i d@ is energized to cause the bimetallic element itil to engage the abutment d@ to close the switch contacts to energize the relay coil it?! to open the valve or cause operation of. the oil burner or stolzer. in this manner, when the room temperature is above a predetermined value, the further supply of heat to the room is prevented and when the temperature is below another predeterminedV lower value, an additional supply oi heat is supplied to the room.4 When the room temperature is between these two predetermined values, the supply of heat to the roomis maintained at a value which is suicient to maintain the temperature in the room between these two values.

The high limit switch t8 is shown in this modication to be connected in the line wire Wt so that when an abnormally high temperature exists within the boiler, thersupply of energy to the motor and the two transformers @te and it@ is cut o' to prevent operation of any portion of the system.

In both systems, it will be noted that the valve or motor broadly represents a condition or force changing device or temperature changing` device and that this condition or force changing device or temperature changingdevice is controlled by' actual values of a condition l(such as room temperatures) and by changes in some condition- (such as boiler temperature) 'produced by the condition or force changing device or in accordance with changes in theoutput or capacity or edectiveness of the condition or force changing device. In the preferred system, the means which is responsive to changes in the condition or force or effectiveness or capacity or output operate to modulate the action of the condition or forc changing device. rIt will also be noted that the systems of the present invention are so arranged that a room thermostat having three positions, namely, a iirst position in which one contact is made, aL second position wherein 'another contact is made, and a third position wherein neither contact is made, and preferably a thermostat ofthe type which alternately engages a pair of contacts and has an intermediate position, operates a mechanical mechanism which is correlated with' anotherv device operative upon changes in the condition or force rather than actual values thereof in such manner that for two of thev room thermostat positions it has absolute control and for the third position the device responsive to changes A takes control.

Many changes in the details of construction and wiring arrangements may of course be made by f those skilled in the art and I therefore intend to be limited only by the scope of the appended claims. i i J I claim as my invention:

1. In a system of the classdescribed, in combination, a condition changing device, means rein the condition or force sponsive to changes in the value of a condition which is directly produced by said condition changing device, control means controlled by said means to operate the condition changing device to maintain said condition at its prevailing value, mechanisms mechanically associated with said means to prevent the same from controlling said control means, and means responsive to another condition in contrai of said mechanism. v

2. In a system oi the class described, in combi nation, a condition changing device, means responsive to changes in the value o a condition Vwhich is directly produced by said condition 3. 1n a system. of -the class described, in combination, a'condition changing device, me re= sponsive to changes in the value of-a Condition which is directly produced by said condition changing device, control means controlled by seid means to operate the condition changing device when the value of said condition lowers a pre` determined amount and to stop operation ci the condition changing 'device when the value of said condition rises a predetermined amount, mechanism mechanically associated with said means to prevent the same from'operating said control means as a result of changes in said condition, and means responsive to another condition' in control of said mechanism.

4. A'system of the clam described, comprising, in combination, a condition changing device, means responsive to changes in the condition of said condition changing device in control oi the condition changing device to control the same to maintainy the value of the condition thereof at the particular value prevailing, and mechanism responsive to another condition to prevent respense 'of said means to changes in the firstnamed condition.

Y 5. A system of the class described, comprising,

in combination, a condition changing device, a i

control member normally moved in accordance with changes in the value of a condition which is aiected by the condition changing device, connections between said control member andcondition changing device by which the former controls the latter to maintain the condition at the particular value prevailing, mechanism associated with said control member and operative to prevent movement thereof upon changes in said condition, and acondition responsive device in,

control of saidmechanism.

6. A system of the class described, comprising,

vin combination, a condition changing device, a

control 'member normally moved in accordance with changes in the value of a' condition which is dition changing device by which the former controls the latter, mechanism associated with said control member and operative to mover the same to either of its extreme control positions and maintain' it therein irrespective of changes in the value 0f said condition, and means responsive to another condition in control of said mechanism and operative to move the same to one of its extreme control positions when the valueoi said second condition rises to a' predetermined maximum and to move the same to its other extreme control position when the value of said second condition falls to a predetermined minimum.

7. In combination, a control device operative to change the value of a condition, an element responsive to changes in said condition, a control member coupled to said element through continuously acting non-positive transmission means whereby said control member normally moves in accordance with the movements of said element, connections between said control member and control device by which the former controls the latter, and means responsive to another condition operative to prevent movement of said control member whereby the position of the control member in relation to the position of said element may be changed so that thereafter the control device is controlled to maintain said rst condition at a new value.

8. In combination, a control device operative to change the value of a condition, an element trols the latter, and means responsive to another condition operative to move said control member to either of its extreme control positions and maintain the same therein irrespective of changes in said rst condition whereby the position of said control member in relation to the position of said element is changed.

9. In combination, a control device operative to change the value'of a condition, an'element responsive to changes in said condition, a control member coupled to said element through continuously acting non-positive transmission means whereby said control member normally moves in accordance with the movements of said element, connections be ween said control member and control device by which the former controls the latter,I electrical means associated with the control member and selectively energizable to move the'control member to one or the other of its extreme control positions and maintain it therein irrespective of changes in the value of said condition, and switching means in control of the energization of said electrical means.

l0. In combination, a control device operative to change the value of a condition, an element responsive to changes in said condition, "a control member coupled to said element through continuously acting non-positive transmission means whereby said control member normally sponsive means responsive to the condition o! moves in accordance with the movements of said element, connections between said control member and control device by which the former controls the latter, a pair of heat responsive devices associated with said control member and operative to move the same to one or the other of its extreme control positions, and means to vary the temperature of said heat responsive devices.

l1. In combination, a control device operative to change the value of a condition, an'element responsive to changes in said condition, a control member coupled to said element through continuously acting non-positivetransmission means whereby said control member normally moves in accordance with the movements of said element, connections between said control member and control device by which the formeronY` trcls the latter, a pair of heat responsive devices associated withsaid control member and operative to move the same to one or the other of its extreme control positions, electrical means to heat each of said heat responsive devices, and switching means responsive to another condition in control of said electrical heatingmeans.

12. In a conditioning system for conditioning a space to be controlled, in combination, a condition changing device for changing the condition of a fluid for changing the condition of such space, means normally movable in accordance with changes in the condition of said iiuid, connections between said means and condition changing device by which the former controls the latter, a pair of heat responsive devices arranged additionally to control said means, a pair of electrical heaters associated with said heat responsive devices, and switchingv means responsive to the condition of said space in control of the electrical heaters.

13.y The combination with a condition changing device, `for changing the condition of a iluid that in turn varies the condition of a space to be controlled, of a control member in control of said condition changing device, condition responsive means responsive to the'condition of said uid, connections between said meansy and control member including slip, friction transmission means whereby the control member is normally moved in accordance with the changes in such condition, and. means responsive to -a condition of the space additionally to control the movements of said control member.

14. The combination withla condition changing device for changing the condition-of a fluid that in turn varies the condition of a space to 'be controlled, of a control member in control of said condition changing device, condition re sponsive means responsive to the condition of 7 said uid, connectionsbetwecn said means and control `member including continuously acting non-positive transmission means whereby the control member is normally moved in accordance with the changes insuch condition, and means responsive to a condition of the space to move I said control member to one or the other of its extreme positions upon rise and fall of the value of said -space condition while permitting movement of said control member by said first condition responsive means when said space condition is at the desired value.

15. The combination with acondition changing device for changing the condition of a, iluidthat in turn varies thecondition of a space to be controlled, of a control member in control of said condition changing device, condition resaid fluid, connections between said means and control member including slip friction transmission means whereby the control member is normally moved in accordance with the changes in such condition, mechanical means with'sald control member and selectively operable to permit movement thereof or to move the same to one oiits extreme control positions and maintain it therein irrespective of changes in the condition of said fluid, and means responsive to a condition of the space in-control of said mechanical means. 4

16. The combination with a condition changing device for changing the condition of a fluid that in turn varies the condition of a space to,be,

associated controlled, of a control member in control of said condition changing device, condition responsive means responsive to the condition of said fluid, connections between said means and control member including slip Yfriction transmission means whereby the control member is normally moved in accordance with the changes in such condition, electrical means associated with said control member and selectively energizable to permit movement of the control member in response to changes in the value of the condition oi! said fluid or to move said control member to an extreme position and maintain the same therein irrespective of changes in the condition of said uid, and current controlling means responsive to changes in a condition of the space in control of said electrical means.

17. The combination with a condition changing device for changing the condition of a fluidv that in 4turn varies the condition of a space to be controlled, of a control member in control of said condition changing device, condition responsive means responsive to the condition of said fluid, connections between said means and control member including slip friction transmission means whereby the control member is normally moved in accordance with the changes in such condition, electrical means associated with said control member and selectively energizable to permit movement of the control member in response to changes in the value of the condition of said iiuid or to move said control member to an extreme position and maintain the same therein irrespective of changes in the condition of said fluid, and double circuit switching means responsive to a condition of said space in control of said electrical means.

18. The combination with a condition changing device for changing the condition of a uid that in turn varies the condition of a space to be controlled, of a control'member in control of said condition changing device, condition responsive means responsive to the condition of said fluid, connections between said means and control member including continuously acting non-positive transmission means whereby the control member is normally moved in accordance with the changes in such condition, means including a vpair of electrical devices selectively energizable to permit movement of said control member in response to changes in the condition of said uid or to move said control member to either of its extreme positions and maintain it therein irrespective of changes in the condition of said fluid, and. double circuit switching means responsive to a condition of said space in control of said electrical devices.

i9. The combination with a condition changing device for changing the condition of' a fluid. that in turn varies the condition of a 4space to be controlled, of a control member in control of said condition changing device, condition responsive means responsive to the condition of said fluid, connections between said means and control member including continuously acting non-positive transmission means whereby the control member is normally moved in accordance with the changes in such condition, means including a pair of electrical devices operable to permit movement of said control member in response to changes in the condition of said uid when both of said devices' are deenergized and to move said control member to one or the other of its extreme positions and maintain it therein upon selective energization of said electrical devices, double circuit switching means responsive to a condition of the space connected to said electrical devices to maintain the same deenergized when the space condition is at the desired value and to energize one or the other thereof if the space condition rises above or falls below said desired value.

20. In combination, a device for changing the condition of a fluid for varying the condition oi a space to be controlled, a control member associated with said device for controlling the same and movable throughout a given control range, an element responsive to a condition of the iiuid, continuously acting non-positive transmission means between the control member and condition responsive element whereby said element may move 'the control member through its control range upon variations in the conditionl of said fluid while relative movement between the control member and condition responsive element is permitted,heat responsive means associated with the control member to prevent its movement in its control range, and means responsive to a condiu tion of the space in control of said heat responsive means.

2l. In combination, a device for changing the condition of a fluid for varying the condition of a space to be controlled, a control member associated'with said device for controlling the same and movable throughout a given control range, an element responsive to a condition of the fluid, continuously acting non-positive transmission means between the control member and condition responsive element whereby said element may move the control member through its control range upon variations in the condition of said iiuid while relative movement between .the control member and condition responsive element is permitted, heat responsive means associated with the control member to prevent its movement in its control range, electrical means for heating said heat responsive means, and current controlling means responsive to variations in the condition of said space in control of said electrical means.

22. In combination, a device for changing the condition of a fluid for varying the condition oi a space to be controlled, a control member associated with said device for controlling the same and movable throughout a given control range, an element responsive to a condition of the uid, continuously acting non-positive transmission means between the control member and condition responsive element whereby said element may move the control member through its control range upon variations in the condition oi said uid while relative movement between the control member and condition responsive elem ment is permitted, a pair of heat responsive devices associated with said control member and operative to permit the same to move throughout its control range or to move the control member to either extreme of its control range and maintain it therein, and means responsive to a condition oi' said space in control of said heat re- Y sponsive devices.

23. In combination, a device for changing the rcondition of a fluid for varying the condition of continuously acting lnon--positive transmission' means between the control member and condition responsive element whereby said element may move the control member through its contive to permit the same to move-throughout its control range or to move the control member to either extreme of its control range and maintain it therein, electrical means for heating said heat responsive devices, and current controlling means responsive to a condition of said space in control of said electrical means.

24. In combination, a device for changing the condition of a iiuid for varying the condition of a space to be controlled, a control member associated with said device for controlling the same and movable throughout a given control range, an element responsive to a condition of the fluid, continuously acting non-positive transmission means between the control member and condition responsive element whereby said element may move the control member through its control range upon variations in the condition of said fluid while relative movement between the control member and condition responsive element is permitted, a pair of heat responsive devices associated with said control member and operative to permit the same to move throughout its control range or to move the control member to either extreme of its control range and maintain it therein, separate electrical heaters for said heat responsive devices, and double circuit switching means responsive to a condition of the space in control of said electrical heaters.-

25. In combination, a device for changing the condition of a fluid for varying the condition of a space to be controlled, a control member associated with said device for controlling the same and movable throughout a given control range, an element responsive to a condition of the fluid, continuously acting non-positive transmission means between the control member and condition responsive element whereby said element may move the control 'member through its control range upon variations in the condition of said fluid while relative movement between the control member and condition responsive element is permitted, a pair of heat responsive devices l associated with said control member and arranged to permit movementthereof throughout its control range when both said heat responsive devices are relatively cold and to move said control device to one or the other of the limits 'of its control range upon selective heating of said heat responsive devices, and means responsive to a condition of the space in control lof the temperature of said heat responsive devices.

26. In combination, a device for changing the condition of a iiuid for varying the condition of a space to be controlled, a control member associated with said device for controlling the same and movable throughout a given control range,

an element responsive to a condition of theuid, continuously acting non-positive transmission means between the control member and condi-'- tion responsive element whereby said element may move the control member through its control range upon variations in the'condition of said fluid while relative movement between the control member and condition responsive element is permitted, a pair of heat responsive devices associated with said control member and arranged vto permit movement thereof throughout its control range when both said heat responsive devices are relatively cold and to move said control device to one or the other of the limits of its control range upon selective heating of said heat responsive devices, separate electrical heaters for said heat responsive devices, and

double circuit switching means responsive to a. condition of said space and connected to said electrical heaters selectively to energize the same as the space condition rises above or falls below a given desired value.

CARL G. KRONMIILER. 

